I hooked up an Oppo 83 to a pre-pro via MCH analog. The pre-pro only has 5.1 in and so I set up the Oppo to downmix 7.1 to 5.1. The speaker setup is 7.1 (using rear surrounds) and Dolby PL IIx is applied. I then played a disk that identified the channels. The rear surround channels played through the respective L or R surround channel speaker. The rear surrounds remained silent. It seems to me that the down mix in the Oppo isn't doing a job as well as it can. Instead of merely redirecting the rear surround to its respective surround channel, it should process a rear surround channel and send appropriate signals to both surround channels such that the application of Dolby PL IIx would then route the signal to the correct rear surround speaker.

You didn't read my post carefully. Of course it can't send a signal directly to the rear surround. But it can process the signal and send appropriate signals to the surrounds such that Dolby PL IIx would direct it to the correct rear surround instead of the surround.

Does your pre-pro redigitize so that it can apply PLIIx to the analog inputs? If not, you'll never get rear channel audio. If so, PLIIx will produce rear channel audio regardless of whether/how the Oppo does the downmixing. But, it is highly unlikely that the Oppo uses PLIIx endoding when downmixing to 5.1. I've never heard of any player doing that. Also, the fact that you are not hearing audio in both surrounds when playing a test disc does not mean that audio is not being sent to both. You are only hearing one channel at a time on the test disc, yes?

You didn't read my post carefully. Of course it can't send a signal directly to the rear surround. But it can process the signal and send appropriate signals to the surrounds such that Dolby PL IIx would direct it to the correct rear surround instead of the surround.

Ed

I did read it sufficiently carefully. The problem lies with your pre/pro, not the player. As others have asked, can it apply DPL to an analog input?

Does your pre-pro redigitize so that it can apply PLIIx to the analog inputs?

Yes. It's an Anthem AVM 20 which is one of the few that can do it.

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But, it is highly unlikely that the Oppo uses PLIIx endoding when downmixing to 5.1. I've never heard of any player doing that.

I think I agree. But at a minimum, it could have easily weighted volumes to L & R surrounds so that a 5.1 speaker system would have phantom imaged between the surrounds, and maybe PL IIx in a 7.1 speaker setup might have redirected to a rear speaker.

I don't think so. The player is down-mixing using the most simple algorithm. It just sends L rear-surround to L surround and R rear-surround to R surround. The pre-pro then does only what it can do - reproduce through the L or R surrounds. The pre-pro has no way to know that these signals originated as rear surrounds.

Wouldn't be the first time something like that was overlooked. Have you tried asking Oppo what their take is? They're probably a small enough company that you'll get an actual answer and not some corporate canned response.

I don't think so. The player is down-mixing using the most simple algorithm. It just sends L rear-surround to L surround and R rear-surround to R surround. The pre-pro then does only what it can do - reproduce through the L or R surrounds. The pre-pro has no way to know that these signals originated as rear surrounds.

Ed

There is no way for the player to do that. What the prepro gets is not encoded 5.1 but analog 5.1 and there is no coding or tagging on it. Thus, it is the prepro that has to reprocess and redistribute the signals in the best way it can. Some will permit redirection and/or redistribution of the (side) surrounds to the rear surrounds.

My Meridian has the options of sending side surround info to the sides, the rears or both from a 5.1 source and/or with DPL IIx. Are there such options on your prepro?

There is no way for the player to do that. What the prepro gets is not encoded 5.1 but analog 5.1 and there is no coding or tagging on it.

I didn't mean to imply digital encoding. I meant that in principle the analog signal can be encoded by phase and amplitude distribution such that the DPL IIx can figure out that the signal should come from the rear surround speaker.

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Thus, it is the prepro that has to reprocess and redistribute the signals in the best way it can.

This is my point. If the down mix simply redirects the rear signal to the surround, the pre-pro cannot distinguish that signal from one that is meant to be in the surround channel. I'm wonder whether it's too much to expect a down mix that is more elaborate.

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Some will permit redirection and/or redistribution of the (side) surrounds to the rear surrounds.

My Meridian has the options of sending side surround info to the sides, the rears or both from a 5.1 source and/or with DPL IIx. Are there such options on your prepro?

No, the Anthem does not do that. But that capability wouldn't really be a solution to the problem here.

Wouldn't be the first time something like that was overlooked. Have you tried asking Oppo what their take is? They're probably a small enough company that you'll get an actual answer and not some corporate canned response.

I haven't asked them. I assume that the down mix is something that is "hard wired" in a chip that they purchase and they have no way of changing it.

Is the Anthem multichannel input set to Analog DIR (direct) or Analog DSP? Sort of assuming DSP since you can apparently overlay PLIIx, but had to ask...

I have an AVM 20 but unfortunately I just took it out of the rotation. Besides, I don't have a player with 7.1 mch outputs to try, only 5.1 mch outputs. However, I'm almost certain, but not quite, that I could apply DPLIIx to the mch analog inputs and get sound from the back as long as mch input was set to Analog DSP.

Also, the Anthem does have provisions to reverse surrounds and rears for the mch inputs and also to copy surrounds to rear if you so desire.

Is the Anthem multichannel input set to Analog DIR (direct) or Analog DSP? Sort of assuming DSP since you can apparently overlay PLIIx, but had to ask...

It is set to Analog DSP.

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However, I'm almost certain, but not quite, that I could apply DPLIIx to the mch analog inputs and get sound from the back as long as mch input was set to Analog DSP.

Yes - I'm not saying that I can't get sound out of the rears with 5.1 analog in - with Dolby PL IIx I do get sound when the input is a movie or a concert disk. The problem is on a test BD when only one rear surround channel is being identified. In other words, the down mixing is not happening in an optimal way. With "random" multichannel audio, someting will stimulate the DPL IIx to put something in the rears.

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Also, the Anthem does have provisions to reverse surrounds and rears for the mch inputs and also to copy surrounds to rear if you so desire.

OK - I set that aspect up a long time ago and don't quite remember. But those are hokie settings IMO.

Are you saying that when the 7.1 BD test disk plays (for example) a tone to the back left speaker it comes out of the back right or both backs or?

The tone for the rear right comes out the right surround speaker in your example. That's because the Oppo's down mix simply redirects the rear right to the right surround. Therefore the Anthem only knows that it's getting a right surround and plays it there as it should. I think that a proper 7.1 to 5.1 down mix should somehow put signal in both the R and L surround channels in such a way that Dolby PL IIx will (mostly, maybe not perfectly) decode it as a rear right channel.

I didn't mean to imply digital encoding. I meant that in principle the analog signal can be encoded by phase and amplitude distribution such that the DPL IIx can figure out that the signal should come from the rear surround speaker.

But won't the PLIIx in the Anthem do that when it sees a real signal with info from both L & R (surround + back) channels to put into the matrix formula?

When it sees complex signals in both L&R channels then invariably something gets routed to the rears. But the way in which the signals are routed is not what is intended by the original 7.1 mix.

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It doesn't do what you want (obviously) but in the end it works out as best the matrix algorithm can with real signals, even though the single channel tone doesn't, yes?

Certainly Dolby PL IIx does the best it can with the signal it gets. But I feel that things have been comprimised. For example, if you had a disk that had a 7.1 mix where a sound is panned across the back from L to R, that pan would not be reproduced faithfully, even though at some point I'm sure sounds would come from the rear surrounds.

No I don't - but then I haven't played with any BD players other than the Oppo. It just seems odd that when the engineers were deciding how to down mix 7.1 to 5.1 they didn't do anything more than simply copy L to L and R to R.

Regarding encoding analog signals, didn't the old Dolby Pro Logic do that to get a center and a mono surround channel?

No I don't - but then I haven't played with any BD players other than the Oppo. It just seems odd that when the engineers were deciding how to down mix 7.1 to 5.1 they didn't do anything more than simply copy L to L and R to R.

I think the downmix was intended only to accommodate 5.1 systems and presumed that those with 7.1 systems would take that directly/discretely and not need the downmix/upmix.

I think the downmix was intended only to accommodate 5.1 systems and presumed that those with 7.1 systems would take that directly/discretely and not need the downmix/upmix.

I feel like I'm beating this to death - so I'll stop soon - but let me just repeat something I said above: Even if you have a 5.1 system, you'd want something originating in one of the rear surround channels to be redirected to a weighted volume between the 2 surround channels so that it phantom imaged behind you instead of to the side surround.

Yeah, I agree you'd want that, but I think it's beyond the scope/intent of what downmix and matrix surround extraction do...not something broken, per se. What you want is a new codec to handle it that way.

I could be mistaken about this, but I don't think playing a test tone for a single channel will ever produce audio from multiple speakers, even when that channel is a proper downmix using surround encoding sent digitally to a processor using ProLogicII.

I could be mistaken about this, but I don't think playing a test tone for a single channel will ever produce audio from multiple speakers, even when that channel is a proper downmix using surround encoding sent digitally to a processor using ProLogicII.

For the case that I'm talking about, I don't see any reason why the proper downmix wouldn't send signals to 2 surround channels. After all, the original mix had a signal to a channel that does not exist in the downsampled space. Clearly, sending the signal completely to one downmixed channel cannot be correct since then it should have been in that channel in the first place.

Anyway, if the downmix is processed in an appropriate way and sent to the 2 surround channels, playback with PL IIx ideally would place it back in the single rear surround channel that it originated in.

For the case that I'm talking about, I don't see any reason why the proper downmix wouldn't send signals to 2 surround channels.

Well, I think it does do that. Material from Left Rear Surround goes to Left Surround and material from Right Rear Surround goes to Right Surround. But, if you are only playing one surround channel at a time, the matrix processor has no way to extract anything. I think you have to play both surround channels together in order to get the extractions for the rears.

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Anyway, if the downmix is processed in an appropriate way and sent to the 2 surround channels, playback with PL IIx ideally would place it back in the single rear surround channel that it originated in.

I suppose PLIIx encoding could do something like that. But, nothing of that sort is happening with a downmix converted to analog. The matrix processor will do the best it can based on comparisons with the material found in the other channels. But, it's not going to be able to produce the kind of output you are describing.

Well, I think it does do that. Material from Left Rear Surround goes to Left Surround and material from Right Rear Surround goes to Right Surround.

I don't know why this is so hard to understand. I'm trying to explain as clearly as I can. When I say that the "proper downmix could be sent to 2 surrounds, I'm talking about the source material originating in one of the rears. Of course when both L & R rears are downmixed, both surrounds get a signal even with the simple scheme that is implemented.

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But, if you are only playing one surround channel at a time, the matrix processor has no way to extract anything. I think you have to play both surround channels together in order to get the extractions for the rears.

I've already said this several times. The problem is not in the pre-pro. The player is down mixing in a trivial way - just copying L rear to L surround and R rear to R surround.

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I suppose PLIIx encoding could do something like that. But, nothing of that sort is happening with a downmix converted to analog.

I realize that this is not happening. I started this thread because I was surprised to discover that the downmix is not this way but instead the trivial copying - which happens to lead to undesirable effects - like poor panning.